Friction clutch driven plates

ABSTRACT

A friction clutch driven plate (10) having a hub (11) and friction facings (14, 15) which face in opposite directions. The friction facings are mounted on respective coaxial annular carrier plates (16, 17) which are rotatable about the hub (11) and are secured back to back with each other by the stop pins (22) which pass through aligned holes (26, 27) in the two carrier plates (16, 17). The holes (27) in at least one carrier plate (17) being enlarged to enable that carrier plate (17) to move rotationally relative to the other carrier plate (16), said relative rotation being resisted by springs (28) acting between the two carrier plates.

This invention relates to friction clutch driven plates for vehicles andin particular to friction clutch driven plates for cars.

A typical motor vehicle engine is connected to the vehicle gear boxthrough a friction clutch which includes a pressure plate and flywheelconnected to the engine, and a clutch driven plate sandwhichedtherebetween which is connected to the vehicle gear box.

In order to smooth out the clutch engagement on take up of the drivefrom the engine, the clutch driven plate generally has some axialcushioning between its opposed friction facings, and a torsion dampingmeans between the friction facings which engage the engine, and thedriven plate hub which is connected to the gear box.

The present invention seeks to provide a different construction ofclutch in which the two friction facings also have some degree oftorsion damping operable therebetween during the clutch take up. Thiswill help prevent clutch judder and give an improved clutch take-up.

Accordingly there is provided a friction clutch driven plate having ahub and friction facings which face in opposite directions, the frictionfacings for each direction are mounted on a respective coaxial annularcarrier plate which is rotatable about the hub, each carrier beingrotatable about the hub, the two carrier plates being secured back toback with each other such that one carrier plate can rotate relative tothe other carrier plate, said rotation being opposed by resilient means.

Preferably the two carrier plates are secured by fastening means passingthrough aligned holes in the two carrier plates, said holes in at leastone carrier plate being enlarged relative to the fastening means toenable said one carrier plate to move rotationally relative to the othercarrier plate, said relative rotation being resisted by resilient meansacting between the two carrier plates.

The relative rotation between the two carrier plates can only occuruntil the clamping load of the clutch springs prevents further relativerotation.

Preferably the carrier plates are annular steel plates with a pluralityof radially projecting circumferentially spaced fingers around the outerperipheral edge thereof, and the friction facings are secured to theprojecting fingers.

Preferably the hub has a radially outwardly extending flange, and thetwo carrier plates are secured by said fastening means to a disc adaptorarranged on one axial side of the hub flange, and the disc adaptor issecured by an axially extending fastening means to a retainer platewhich is located on the other axial side of the flange, the axiallyextending fastening means passing through co-operating apertures in thehub flange which allow the disc adaptor and retainer plate to moverotationally about the hub, said rotational movement being resilientlyopposed by torsion damping springs housed in aligned spring windows inthe hub flange, disc adaptor, and retainer plate.

The fastening means, conveniently a rivet, utilised for holding the discadaptor to the retainer plate may also be used to secure the carrierplates to the disc adaptor.

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 is an elevation of a friction clutch driven plate according tothe invention.

FIG. 2 is a section on the line II--II of FIG. 1 also showing aflywheel, pressure plate, and spring in broken lines.

FIG. 2A is a fragmentary cross-sectional view showing friction facingsadhesively attached to carrier plates.

FIG. 3 is an elevation of the fixed carrier plate of the driven plate ofFIG. 1.

FIG. 4 is an elevation of the movable carrier plate of the driven plateof FIG. 1.

FIG. 5 is an elevation of the hub flange.

FIG. 6 is an elevation of the disc adaptor.

FIGS. 7a, 7b and 7c and 8a and 8b are schematic drawings showing therelationship between the spring windows of the various moving parts ofthe driven plate.

With reference to FIGS. 1 to 6 of the accompanying drawings, theillustrated friction clutch driven plate 10 comprises a hub 11 havinginternal splines 12 for connection with a gear box input shaft (notshown) and a radially outwardly extending annular flange 13.

A pair of annular friction facings 14 and 15 are each mounted on anannular carrier plate 16 and 17 respectively. Each carrier plate 16 and17 is an annular plate having a plurality of circumferentially spacedradially extending fingers 18 projecting outwardly from its outerperiphery.

The facings 14 and 15 are secured to the fingers 18 of the respectivecarrier plate 16 or 17 by any suitable means e.g. rivets, integralrivets, tabs, adhesives. It has been found that silicone rubber adhesive20 as shown in FIG. 2A which is laid onto the back face of the facing 15in concentric circles, or spiral turns, is particularly suitable. Thereader is directed to U.S. Pat. No. 4,821,860, U.S. Pat. No. 5,076,410and pending U.S. Ser. No. 488,050 for a more detailed description of theadhesion of facings to a carrier plate of the present type usingsilicone rubber adhesives. In particular it is advantageous to use asilicone rubber adhesive 20 for the facing 15 adjacent the pressureplate P and a conventional rigid adhesive 20A for the facing 14 adjacentthe flywheel F.

The carrier plates 16 and 17 are flat steel plates that are arrangedback to back with the facings 14 and 15 directed in opposite directionsfor engagement in use with a flywheel F and pressure plate P. The twocarrier plates 16 and 17 are located on one axial side of the hub flange13 and are secured to a disc adaptor 21 located axially outwardly of thecarrier plates 16 and 17 by four equiangularly spaced rivets or stoppins 22. The stop pins 22 also serve to secure the disc adaptor 21 to aretainer plate 23 located on the other axial side of the hub flange 13.The stop pins 22 pass through co-operating apertures 24 in the outerperipheral margin of the hub flange 13 so that the carrier assemblycomprising the carrier plates 16, 17, disc adaptor 21, and retainerplate 23, can rotate relative to the hub 11.

The relative rotation is limited by abutment of the stop pins 22 withthe radial ends of the apertures 24. The entire carrier assembly may bemounted to facilitate rotation on a bush 25 located between the hub 11and the retainer plate 23.

The two carrier plates 16 and 17 are arranged so that one carrier plate16 is fixed rotationally fast with the disc adaptor 21 by the stop pins22 closely engaging in holes 26 in the plate 16, whereas the secondcarrier plate 17 is capable of limited angular rotation relative to thefirst carrier plate 16. This rotation is allowed by the pins 22 beingaccommodated by circumferentially elongated holes 27 in the plate 17,which allow for approximately 5 degrees of movement between the twocarrier plates 16 & 17 in either direction of rotation, and for rotationof the second carrier plate 17 relative to the hub 11.

This arrangement could be reversed with the carrier plate 17 fixed onthe stop pins 22 and the carrier plate 16 having the elongated holestherein to allow it to move around the hub. In yet a further embodiment,both carrier plates could have elongated apertures therein allowing eachplate some limited circumferential movement.

The relative rotation of the friction facings 14 and 15 relative to thehub 11 is resisted by resilient means, preferably springs 28, housed inaligned sets of apertures 29, known as spring windows, in the hub flange13, carrier plates 16 and 17, disc adaptor 21, and retainer plate 23. Inthe present embodiment there are four springs 28 housed in four sets ofapertures 29 but other numbers of springs could be used, e.g. three toeight springs.

Each set of apertures 29 comprises a disc adaptor spring window 31, afixed carrier plate spring window 32, a movable carrier plate springwindow 33, a hub flange spring window 34, and a retainer plate springwindow 35.

The springs 28 comprise two diametrically opposed light torsion dampingsprings 28A, and two diametrically opposed main torsion damping springs28B. The light torsion damping springs 28A act to resist relativerotation initially between the two carrier plates 16 and 17, andthereafter between the carrier assembly and the hub 11.

The main torsion damping springs 28B act to resist relative rotationbetween the carrier assembly and the hub 11.

The light damping springs 28A are each housed in set of apertures 29Asuch that the respective carrier plate windows 32A, 33A, disc adaptorwindow 31A, and retainer plate window 31A all have the samecircumferential length and in the `at rest` position are all inalignment. The spring 28A is a tight fit in the set of apertures. Thisis shown schematically in FIG. 7(A). The respective hub flange window34A is circumferentially longer than the other windows in the respectiveset 29A by an equivalent to 5 degrees of relative rotation at each endof the window.

The main torsion damping springs 28B are each housed in a set ofapertures 29B such that the respective disc adaptor windows 31B, fixedcarrier plate window 32B, hub flange window 34B, and retainer platewindow 35B all have the same circumferential length and are all inalignment in the `at rest` position. The main springs 28 B are a tightfit in the set of apertures. This is shown schematically in FIG. 8A. Therespective moving carrier plate window 33B is circumferentiallyelongated compared with the other windows in the respective 29B set byan equivalent of about 5 degrees relative rotation at each end.

The operation of the friction clutch driven plate will now be describedwith the hub held stationary and a torque load applied to the frictionfacings to rotate the facings in the direction of arrow `A` as shown inFIG. 1.

During the take up of the clutch, as the friction facings begin tofrictionally engage between the pressure plate P and the flywheel Funder the clamp load of the spring S (see FIG. 2), the friction facing15 adjacent the pressure plate will normally engage first fractionallybefore the other facing engages with the flywheel.

As the friction facings 15 engage the pressure plate, the torsion loadwill rotate the moveable carrier plate 17 relative to the fixed carrierplate 16 which is held stationary relative to the hub 11 by the maintorsion springs 28B engaging in the fixed carrier plate spring windows32B. As the carrier plate 17 is rotated the light springs 28A arecompressed between opposed radial faces in the spring windows 31A, 32A,and 35A, in the fixed carrier plate 17, the disc adaptor 21, andretainer plate 23, on the one hand, and the opposed radial face in themoveable carrier plate spring window 33A. This is shown schematically inFIG. 7(B).

Simultaneously, the clearance `C` in the spring window 33B around themain torsion damping springs 28B, allows the moveable carrier plate 17to rotate without interference from the main spring 28B until, theclearance `C` has been taken up.

This is shown in FIG. 8B, and coincides with the position when themoveable carrier plate 17 engages the stop pins 22 through the ends ofthe apertures 27 and the relative position between the two carrierplates is then fixed, so that any further rotational movement of thefacing 15 will also cause the carrier plate 16 to rotate and both plateswill move together without further compression of the light spring 28Auntil the light spring 28A abuts the end of the hub aperture 34A.

The degree of rotation at which spring 28A comes against the end of hubflange window 34A may coincide with the abutment of the moveable carrierplate window 33B against the main torsion damping springs 28B (see FIG.8B), and the abutment of the stop spring 22 against the ends of theapertures 27.

However the various clearances can be altered as is desired to achieve arequired torque verses relative rotation curve.

Once the two carrier plates 16 and 17 are rotationally fixed, either bythe abutment of the stop pins 22 against the ends of the apertures 27,or by the application of a sudden and large spring clamp load, thenfurther rotation of the carrier assembly around the hub is resisted byall the springs 28 in the well known manner.

In an alternative embodiment (not shown), the clutch driven plate has anidle centre for damping out vibratory oscillations associated withgearbox idle rattle. Such a driven plate is illustrated in WO 88/08092.

Instead of the movable carrier plate 17 operating against low ratesprings 28A housed in spring apertures in the main hub flange 13, themoving carrier plate could be arranged to operate against `low rate`springs associated with the idle centre.

In yet a further embodiment the two carrier plates 16 and 17 could bearranged so that the fingers 18 are spring fingers which are shaped sothat the facings 14 and 15 are spaced axially apart with the carrierplates providing some resilience when the facings are clamped together.

I claim:
 1. A friction clutch driven plate having a hub, two annularcoaxial carrier plates, and a pair of annular friction facingscomprising a first facing and a second facing which face in oppositedirections, the first friction facing for one direction being mounted ona respective one of said annular carrier plates, and the second frictionfacing for the other direction being mounted on the other of saidannular carrier plates, each carrier plate being rotatable about thehub, the two carrier plates being secured back to back in contact witheach other such that the carrier plates can rotate relative to eachother, said relative rotation between the carrier plates being opposedby resilient means.
 2. A friction clutch driven plate as claimed inclaim 1, wherein the two carrier plates are secured back to back witheach other by fastening means passing through aligned holes in the twocarrier plates, said holes in at least one carrier plate being enlargedrelative to the fastening means to enable said one carrier plate to moverotationally relative to the other carrier plate, said relative rotationbeing resisted by resilient means acting between the two carrier plates.3. A friction clutch drive plate as claimed in claim 2 and in which thehub has a radially outwardly extending flange, and the two carrierplates are secured by said fastening means to a disc adaptor arranged onone axial side of the hub flange, and the disc adaptor is secured by anaxially extending fastening means to a retainer plate which is locatedon the other axial side of the flange, the axially extending fasteningmeans passing through co-operating apertures in the hub flange whichallow the disc adaptor and retainer plate to move rotationally about thehub, said rotational movement being resiliently opposed by torsiondamping springs housed in aligned spring windows in the hub flange, discadaptor, and retainer plate.
 4. A friction clutch driven plate asclaimed in claim 3 wherein the fastening means utilised for securing thecarrier plates to the disc adaptor are also utilised to secure the discadaptor to the retainer plate.
 5. A friction clutch driven plate asclaimed in claim 4 wherein the two carrier plates are located axiallybetween the disc adaptor and the hub flange.
 6. A friction clutch drivenplate as claimed in claim 3 wherein the two annular carrier platesextend radially inwardly to the hub and also have spring windows thereinwhich align with the other said spring windows so that the carrier platespring windows can accomodate the torsion damping springs.
 7. A frictionclutch driven plate as claimed in claim 6 wherein the relativerotational movement between the carrier plates is resisted by at leastone spring housed in a set of said spring windows.
 8. A friction clutchdriven plate as claimed in claim 7 wherein main torsion damping springsare housed in aligned sets of spring windows in the carrier plates, discadaptor, retainer plate and hub flange, and in each set of springwindows, the windows all have the same circumferential length exceptingthe windows in said one carrier plate which are circumferentiallyelongated, and the spring acting between the carrier plates is alsohoused in a set of spring windows in which the windows all have the samelength excepting the bub flange window which is circumferentiallyelongated.
 9. A friction clutch driven plate as claimed in claim 8wherein for each set of main torsion damping spring windows the moveablecarrier plate window is elongated by 5 degrees of movement at eachcircumferential end relative to the other spring windows in said set ofwindows.
 10. A friction clutch driven plate as claimed in claim 5,wherein the moveable carrier plate is adjacent the hub flange.
 11. Afriction driven plate as claimed in claim 2 wherein the carrier platesare annular steel plates with a plurality of radially projectingcircumferentially spaced fingers around the outer peripheral edgethereof, and the friction facings are secured to the projecting fingers.12. A friction clutch driven plate as claimed in claim 11, wherein atleast one of the friction facings is secured to its respective carrierplate by means of an elastomeric adhesive material.
 13. A frictionclutch driven plate as claimed in claim 12 wherein the adhesive is asilicone rubber adhesive.
 14. A friction clutch driven plate as claimedin claim 2, wherein one friction facing is secured to its respectivecarrier plate by means of an elastomeric adhesive material and the otherfriction facing is secured to its respective carrier plate by a rigidadhesive.
 15. A friction clutch driven plate as claimed in claim 14,wherein the other facing is in use, to be adjacent a flywheel of aninternal combustion engine.